Body weight in mammals is defended so that small changes in weight evoke neuroendocrine and metabolic responses that encourage a return to one’s previous weight. While these homeostatic responses have been more commonly studied in the case of weight loss, our lab has developed a mouse model of overfeeding to study the physiology of defense against weight gain. In response to overfeeding-induced weight gain, the return to previous body weight is mediated primarily by a striking reduction in food intake, which persists until pre-overfeeding body weight is restored. However, preliminary data do not suggest activation of anorectic POMC neurons which reduce food intake or inhibition of the appetite stimulating AgRP or NPY neurons in the arcuate nucleus of the hypothalamus. Furthermore, we found that adipose tissue from overfed mice does not show the same inflammatory response as mice that have become obese slowly due to ad libitum high-fat diet (HFD) consumption. Paradoxically, despite the existence of mammalian systems that defend against weight gain, average body weight in humans has been on the rise over the last half century. Concomitant with the rise in obesity rates, has been increasing availability and consumption of processed and fast foods which are generally high in sugar, salt, and fat making them extremely palatable and calorically dense. Both the caloric density and enticing taste of the foods have been implicated in causing overconsumption and contributing to a rise in average body weight and prevalence of obesity. Thus, while controlling for caloric density we have investigated whether diet palatability can increase body weight and suppress defense against weight gain in mice. We designed our studies so that all diets were of the same caloric density and therefore varied only proportion of calories derived from fats, carbohydrates, and protein. Palatability is the relative subjective preference of one food over another; in our mouse studies we equated preference, when given, a choice with palatability. We confirmed that liquid diets sweetened with sucrose or the non-nutritive sweeteners sucralose and saccharin were preferred over non-sweetened diets. In 12 day feeding studies, although we found that sweetened diets were more palatable than unsweetened diets, they did not increase caloric intake or body weight. Next, we tested whether increasing percent calories from fat leads to increases in palatability or caloric intake. In a similar 12 day feeding preference study, we found diets higher in percent calories from fat (high-fat diet = HFD) were preferred to diets with lower percent calories from fat (low-fat diet = LFD) and that the access to a HFD increased caloric intake and body weight. Employing a four-week single diet feeding study, we also found a linear relationship between percent calories from fat and caloric intake consistent with our hypothesis that percent calories from fat is sensed and modulates caloric intake. To test whether HFD can suppress defense of body weight, we used an overfeeding paradigm which I help develop, to test whether ad libitum access to a HFD prevented a return to the original body weight following overfeeding. HFD did attenuate the hypophagic response to overfeeding and prevented a return to each mouse’s initial weight with the mice having access to the HFD mice stabilizing at a higher body weight. Palatability has traditionally been ascribed to sensing of smell and taste, however, macronutrients can also be sensed within intestinal tract. To determine whether the effects of percent calories from fat require naso-oral sensing to modulate feeding behavior, we used an intragastric feeding system to bypass taste and smell and deliver HFD directly into the stomach of mice. Even in the absence of oropharyngeal sensing, HFD in the gut was sufficient to increase ad libitum caloric intake of a low-fat diet and increase body weight. Finally, based on our findings of post-oral fat sensing driving caloric intake, we tested whether post-oral sensing of percent calories from fat was sufficient to condition a flavor preference. However, we found that when caloric density was controlled, a high percent calories from fat was not sufficient to condition a flavor preference.

Overweight and obesity are prevalent public health problems that impact physical, mental, and social health. Many studies have evaluated weight loss treatments, but most individuals are unsuccessful at maintaining weight loss long-term. Behavioral and cognitive interventions may be effective in promoting weight loss and weight loss maintenance. One cognitive intervention that has shown potential success in reducing weight and caloric intake is inhibitory control training (ICT). ICT involves trainings where individuals are asked to repeatedly withhold dominant responses to unhealthy or high-calorie food images in an effort to increase food-related inhibitory control abilities. Reductions in caloric intake or weight may occur after as little as one week of ICT; however, it is unclear how more frequent ICT sessions promote weight loss and reduce caloric intake. Further, studies on food-specific ICT are generally poorly powered and it is unclear how ICT affects underlying cognitive and neural mechanisms. One way to measure inhibitory control processes is through the N2 component of the scalp-recorded event-related potential (ERP). The amplitude of the N2 ERP component tends to be larger (i.e., more negative) when an individual inhibits a dominant response during go/no-go tasks compared to non-inhibition go trials. I conducted a quasi-randomized controlled trial where 100 individuals with overweight or obesity were assigned to either a generic (active control; n = 48) or food-specific ICT (experimental group; n = 52). ICTs were completed four times per week for four weeks. Weight and caloric intake were obtained at baseline, immediately after four-weeks of ICT, and at a 12-week follow-up. Participants also completed a high-calorie and a neutral go/no-go task while electroencephalogram (EEG) was recorded at each visit. Results from mixed model analyses suggest that neither weight, caloric intake, nor N2 ERP component amplitude towards high-calorie foods changed at post-testing or at the 12-week follow up for either group. Regression analyses suggest that individuals with lower baseline levels of inhibition may show greater weight loss and reductions in caloric intake after a generic ICT, while individuals with higher baseline levels of inhibition may show greater weight loss and reductions in caloric intake after a food-specific ICT. Self-report ratings indicated the appetitive drive towards food decreased over the course of the study, particularly for individuals with higher levels of baseline inhibition. Overall, generic- or food-specific ICT did not affect weight, caloric intake, or food-specific N2 ERP amplitude. Food-specific ICT may be more effective in reducing caloric intake and weight for individuals with larger inhibition responses to food stimuli, while generic ICT may be more effective in reducing caloric intake and weight for individuals with smaller inhibition responses to food stimuli. ICT may also be targeting other mediating processes, such as the appetitive value of food, as opposed to improving food-specific inhibitory control.

Thesis (M. Com. (Business Management)) -- University of Limpopo, 2021 / The trend towards healthy eating has been gradually growing in South Africa. Health consciousness has become more apparent with customers not only wanting to consume quick and convenient meals, but also meals that are nutritionally beneficial. Although fast-food outlets have risen to the occasion by providing for this demand, there are few studies in South Africa that focus on strategic guidelines for fast-food outlets to enable strategic planning for achieving customer satisfaction and the increase in profits with healthier food options on the menu. The purpose of this study was to explore strategic guidelines for customer satisfaction with healthier diet menu items in fast-food franchising outlets in South Africa. An extensive literature review was conducted on the South African fast-food industry and customer satisfaction. The study followed a quantitative method approach, and 400 respondents were selected using the convenience sampling method. An empirical study was conducted in which data was collected from 329 customers of fast-food outlets within the Capricorn Municipality, South Africa by means of self-administered questionnaires. The findings of this study reveal that there is a general level of satisfaction amongst South African customers with the healthier food options available at fast-food outlets with areas of improvement for price, convenience and atmosphere pertaining to healthier diet meals. The study made recommendations on a variety of healthy menu items, interaction between managers and customers, price and value, extended service hours, safe parking and walking distance, cleanliness, staff appearance and dining-in feeling and provided a model on Strategic Sustainable Growth as a guideline to increasing customer satisfaction with healthier diet menu items.

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